Enhanced biosorption of metal ions from wastewater by Fenton modified Hydrilla verticillata   dried biomass

Present study deals with the biosorption of metal ions (Cu²⁺, Zn²⁺, Pb²⁺, and Cd²⁺) from aqueous solutions as well as from wastewater using Fenton modified Hydrilla verticillata dried biomass. Fenton modification process was optimized by varying different parameters such as pH, temperature, contact time, and Fe²⁺/H₂O₂ ratio. The modified biosorbent was characterized by using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and Malvern particle size analyzer. Energy-dispersive X-ray spectroscopy analysis revealed the enhancement in weight percent of Cu²⁺ (47.53 %), Zn²⁺ (41.82 %), Pb²⁺ (43.76 %), and Cd²⁺ (43.15 %) ions on the surface of modified biosorbent after the biosorption process. The experimental data obtained from the batch study were modeled using Langmuir and Freundlich isotherm models. Experimental data showed best fitting to Freundlich isotherm model. The increase in biosorption capacity after the Fenton modification was observed, which follows the sequence: Cu²⁺>Pb²⁺>Cd²⁺>Zn²⁺. The biosorption process followed the pseudo-second-order kinetics, suggesting that the chemisorption may be the rate-limiting step in this study. The thermodynamic study revealed that the biosorption process was spontaneous and exothermic in nature. The biosorption capacity for multi-metal solution was found to be relatively lower than the single-metal solution. Performance of batch reactor in treating wastewater showed significant increase in removal efficiency of Cu²⁺ (from 74 to 96 %), Zn²⁺ (from 67 to 84 %), Pb²⁺ (from 71 to 92 %), and Cd²⁺ (from 71 to 89 %) ions after the modification of biosorbent as compared to raw biomass.